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Purpose Chronic thromboembolic pulmonary hypertension (CTEPH) is a debilitating disease, for which the underlying pathophysiological mechanisms have yet to be fully elucidated. In recent years, microRNAs have emerged as important players in regulation of physiological processes, and dysregulation of microRNA expression has been linked to various diseases. So far, only a limited number of studies has investigated microRNAs in CTEPH. Therefore, the aim of this study was to investigate whether microRNAs are also detectable in tissue specimens obtained from patients undergoing pulmonary endarterectomy (PEA), since differential expression in the tissues could suggest a role of these microRNAs in disease development. Methods Tissue specimens were obtained from patients 16 patients undergoing PEA at the University Hospital Zurich, between 2016 and September 2018. RNA was extracted from FFPE blocks, and expression levels of three microRNAs identified as potential players in CTEPH development through a study of circular RNAs (Miao et al, Medicine 2017), miR-939, miR-942 and miR-92a-2-5p, were measured by microRNA-specific RT-qPCR. In addition, miR-210, the most important microRNA in regulation of hypoxia was measured. Expression of microRNAs was correlated to various clinical factors. Results Of the three miR-candidates measured in plasma before, miR-939 and miR-942 were detectable in PEA tissue specimens. In addition, the hypoxamiR miR-210 was also detectable and represented the microRNA with the highest expression levels. Expression of miR-939 showed a significant negative correlation with peripheral oxygen saturation (p=0.03; Spearman's R=-0.548) and pulmonary vascular resistance (p=0.05, R=-0.502), while miR-942 expression negatively correlated with Jamieson Classification (p=0.04, R=-0.623). Conclusion This pilot study has shown for the first time that microRNAs are readily detectable in material extracted during PEA. Our data shows that microRNAs are differentially expressed between different patients, and that microRNA expression is correlated with various factors of clinical presentation. Thus, our data highlight that microRNA expression warrants further investigation as their dysregulation might be involved in the development of CTEPH.

Background The use of non-heart-beating donors (NHBDs) is an alternative strategy to increase the limited number of donors. The ex vivo evaluation has been proposed to assess the function of the lungs from NHBDs as an interim evaluation of the graft before transplantation. We evaluated the effect of a fibrinolytic agent, urokinase, in a pig ex vivo evaluation model. Methods Domestic pigs (30–38 kg) were divided in 3 groups of 5 pigs each. In the Control Heart-Beating Donor (HBD) Group, the lungs were flushed, explanted, and stored in cold solution (4°C) of low potassium dextran for 4 hours. The pigs in the other 2 study groups were non-heart-beating donors (NHBD), and their lungs were topically cooled for 1 hour in the closed chest after 3 hours of warm ischemia. Urokinase (100,000 IU) was added into the perfusate during reperfusion 1n 1 of the NHBD groups (NHBD-UROK). Hemodynamic and aerodynamic parameters were measured. The wet-to-dry weight ratio was calculated. Results There was a significant difference between NHBD-UROK and NHBD Groups in pulmonary vascular resistance (22.5 ± 3.06 vs 39.02 ± 6.6 Wood Units, p = 0.032), partial pressure of arterial oxygen/fraction of inspired oxygen (250.8 ± 23.3 vs 148.9 ± 14.6 mm Hg, p = 0.032), oxygenation index (6.9 ± 0.7 vs 15.9 ± 3.2, p = 0.016), and wet-to-dry weight ratio (5.99 ± 0.2 vs 7.74 ± 0.3, p = 0.016). Pulmonary vascular resistance did not differ between the HBD and NHBD-UROK Groups but was significantly higher in the NHBD Group than in the HBD Group ( p = 0.032). Conclusion Adding urokinase into the perfusate during ex vivo evaluation resulted in improved graft function by reducing pulmonary vascular resistance and increasing oxygenation after 3 hours of warm ischemia. This ex vivo evaluation model is feasible and may be used to recondition grafts from NHBDs.

Background CD26/DPP IV is a T-cell-membrane protein that cleaves dipeptides from extracellular peptides. Inhibition of its enzymatic activity using Pro-Pro-diphenylphosphonate derivatives has been shown to abrogate acute and accelerated rejection in models of cardiac and pulmonary allotransplantation. Here we investigated the effects of enzymatic DPP IV inhibition on ischemia/reperfusion (I/R) injury after extended ischemia before pulmonary transplantation. Methods A syngeneic rat orthotopic left-lung transplantation model was used. Group I donor lungs (controls) were flushed and preserved in Perfadex for 18 hours at 4°C and then transplanted and reperfused for 2 hours. Group II grafts were perfused with and stored in Perfadex + 25 μmol/liter AB192 [bis(4-acetamidophenyl) 1-( S )-prolylpyrrolidine-2( R , S )-phosphonate]. Group III lungs were perfused with Perfadex + AB192, and stored in Perfadex. After 2-hour reperfusion, oxygenation, peak airway pressure (PawP), graft wet/dry (W/D) weight ratio, myeloperoxidase activity, thiobarbituric acid–reactive substances, graft specific DPP IV enzymatic activities and histomorphology were analyzed. Results AB192 perfusion significantly reduced DPP IV intragraft enzymatic activity in Groups II and III. Compared with controls, transplants from Groups II and III showed significantly improved oxygenation capacity, PawP and W/D weight ratio, with lower intragraft lipid peroxidation; and preserved histologic structure. Conclusions Targeting intragraft DPP IV enzymatic activity attenuated post-transplantation I/R injury and preserved early graft function after extended ischemia.

CD26 is a T-cell co-stimulator, and interacts with adenosine deaminase, human immunodeficiency virus (HIV) Tat-1 protein and extracellular matrix. It possesses dipeptidylpeptidase IV (DPP IV) catalytic activity, which is linked to its co-stimulatory efficacy. We investigated the effect of specific DPP IV systemic activity inhibition on acute pulmonary rejection.Rat single-lung transplantation (Tx) was performed (LBNF1/LEW donor/recipient) in two groups (n = 12). Group I (n = 6) received daily treatment with a Pro-Pro-diphenylphosphonate derivative (AB197), and Group II served as an untreated control. At Day 5 post-Tx, ventilatory parameters, cytotoxicity and mixed lymphocyte reaction were analyzed and staining for ISHLT rejection grade and proliferating cell nuclear antigen (PCNA) was performed.Treatment with AB192 abrogated acute rejection and preserved pulmonary function up to Day 5 post-Tx for PO2 (Group II: 24.9 +/- 6.9 mm Hg; Group I: 149.5 +/- 24.3 mm Hg; p0.001), PCO2 (Group II: 53.3 +/- 13.6 mm Hg; Group I: 39.0 +/- 9.8 mm Hg; p0.05) and peak airway pressure (Group II: 50.7 +/- 17.2 mm Hg; Group I: 20.2 +/- 10.0 mm Hg; p0.01). Controls showed moderate/severe rejection (ISHLT Grade A2 or 3), grafts from inhibited hosts revealed no/mild rejection (Grade A0 to 2: Group II: 2.8 +/- 0.3; Group I: 1.25 +/- 1.0; p0.005). Proliferating cell nuclear antigen (PCNA) staining of rejection-associated cellular infiltrates showed a significant reduction in positivity in perivascular infiltrates (34 +/- 11.5%; p0.05) and bronchial surface epithelium (31.7 +/- 10.6%; p0.05) in Group I vs Group II (55.9 +/- 8.4% and 57.2 +/- 4.5%).Irreversible enzymatic inhibition of DPP IV has been shown to abrogate acute pulmonary rejection, maintain pulmonary function, and preserve histomorphologic architecture. These results extend earlier findings and illustrate the role of CD26/DPP IV in alloantigen-mediated immune responses.

Stenoses of multiple peripheral pulmonary artery branches represent a rare cause of pulmonary hypertension in children, but the prognosis is very poor for such patients. Herein we describe 2 patients with multiple peripheral pulmonary artery stenoses (MPPAS) presenting with severe pulmonary arterial hypertension in adulthood, which has only once been described previously. Both patients lived without significant health problems for decades; however, after onset of symptoms, their medical condition declined rapidly, necessitating lung transplantation several months after the diagnosis despite vasodilator therapy. Because MPPAS mimics chronic thromboembolic pulmonary hypertension, this entity may being underdiagnosed, decreasing the possibility of adequate therapy.

Background Ischemia–reperfusion injury remains an important obstacle to successful lung transplantation. Trimetazidine is an anti-ischemic drug that restores the ability of ischemic cells to produce energy and reduces the generation of oxygen-derived free radicals. The aim of this study was to assess the protective effect of trimetazidine after prolonged ischemia in lung transplantation. Methods Rat single-lung transplantation was performed in 4 experimental groups (n = 5 each). In all groups, transplantation was performed after 18 hours of cold (4° C) ischemia. All donor lungs were flushed with low-potassium dextran–glucose (LPDG) solution that also contained 500 μg/liter prostaglandin estradiol (E 1 ). Groups studied included: Group I: flush solution was administered containing 10 −6 mol/liter trimetazidine (TMZ), neither donor nor recipient treatment given; Group II: donors were treated with 5 mg/kg intravenous TMZ 10 minutes prior to harvest, but the flush solution did not contain TMZ; Group III: recipients treated with 5 mg/kg intravenous TMZ 10 minutes before reperfusion, and flush solution contained 10 −6 mol/liter trimetazidine; Group IV: ischemic control group. After 2 hours of reperfusion, oxygenation was measured and lung tissue was frozen and assessed for adenosine triphosphate (ATP) content, myeloperoxidase (MPO) activity and thiobarbituric acid–reactive substances (TBARS). Peak airway pressure (PawP) was recorded throughout the reperfusion period. Results Group III showed significantly higher levels of ATP content (11.1 ± 5.01 pmol vs Group I, 3.36 ± 1.8 pmol, p = 0.008; vs Group II, 4.7 ± 1.9 pmol, p = 0.03; vs Group IV, 0.7 ± 0.2 pmol, p = 0.008), better oxygenation (442.5 ± 26.5 mm Hg, vs Group I, 161.06 ± 54.5 mm Hg; vs Group II, 266.02 ± 76.9 mm Hg; vs Group IV, 89.4 ± 14.7 mm Hg, p = 0.008) and reduced lipid peroxidation (TBARS) (0.15 ± 0.03 nmol/g; vs Group I, 1.04 ± 0.76 nmol/g; vs Group II, 0.69 ± 0.4 nmol/g; vs Group IV, 2.29 ± 0.4 nmol/g, p = 0.008). PawP and MPO activity were comparable in the 4 study groups. Conclusion Recipient treatment with TMZ provided significant protection of energy status, better oxygenation and reduced lipid peroxidation. Our data suggest that TMZ may be an important adjunct in the prevention of post-transplant lung ischemia–reperfusion injury.

Substitution of the NO-pathway reduces ischemia/reperfusion injury following lung transplantation. 8-Br-cGMP is a membrane permeable analogue of cGMP, the second messenger of NO. In this study the effect of continuous administration of 8-Br-cGMP on early graft function was evaluated. Methods Unilateral left lung transplantation was performed in 10 weight-matched pigs (23–30 kg). Donor lungs were flushed with 1.51 cold (1° C) LPD solution and preserved for 20 hours. In Group I ( n = 5), 8-Br-cGMP (0.2 mg/kg/h) was given continuously over the entire observation time starting 15 min before reperfusion. Group II served as control, no 8-Br-cGMP was administered. In both groups, 250 μg PGE 1 was injected into the pulmonary artery (PA) before flush. One hour after reperfusion the recipients contralateral right PA and bronchus were ligated to assess isolated graft function only. Extravascular lung water index (EVLWI), pulmonary vascular resistance, mean PA pressure, mean systemic arterial pressure and gas exchange were assessed during a 5-hour observation period. Lipid peroxidation as indicator for free radical mediated injury and neutrophil migration to the allograft were measured at the end of the assessment. Results EVLWI was significantly reduced in animals treated with 8-Br-cGMP (overall difference P = 0.024) with a peak 2 hours after reperfusion (Group I, 8.2 ± 0.3 mg/ml vs Group II, 10.1 ± 0.6 mg/ml; P = 0.039). Also in Group I the free radical mediated tissue injury was significantly lower when compared to Group II (Group I, 61.8 ± 12.3 pmol/g vs Group II, 120.7 ± 7.2 pmol/g; P = 0.006). A tendency towards a reduced neutrophil migration after 8-Br-cGMP infusion was shown; however, the changes in comparison to the control animals were not statistically significant (Group I, 1.0 ± 0.2 ΔOD/mg/min vs Group II, 1.7 ± 0.3 ΔOD/mg/min; P = 0.13). Pulmonary- and systemic hemodynamics, and allograft gas exchange did not differ between groups. Conclusions The results indicate that substitution of the NO pathway by administration of the second messenger cGMP at the time of reperfusion improves post-transplant lung allograft function.

Purpose: The number of available donor lungs is still the limiting factor in lung transplantation. We have recently shown during ex-vivo lung evaluation that diluted surfactant lavage improved the graft function after gastric acid aspiration. In the present study we hypothesized that the same treatment in lungs injured by gastric acid aspiration may improve graft function in transplanted porcine lungs. Methods and Materials: Lung injury was induced by intratracheal instillation of 1 ml/kg Oroacid® by a flexible fiberoptic bronchoscope under direct vision into the left main bronchus and the animals were ventilated for 24 hours thereafter. Following harvest the donor lungs were stored at 4°C for 4 hours. In control group (n 4) left lung transplantation was performed without any treatment. In surfactant treated group (n 6) the recipients received intratracheal diluted surfactant (1 ml/kg) lavage just before reperfusion and ventilation. During 7 hours of reperfusion hemodynamic and ventilatory variables were recorded hourly. Bronchoalveolar lavage (BAL) was performed at the end of the experiment for bubble surfactometry and further analysis. Results: Surfactant lavage resulted in lower mean pulmonary artery pressure, lower airway pressure and better oxygenation compared to control group (p 0.001). BAL IL-6 level and neutrophil percentage at the end of the experiment was significantly higher in control compared to surfactant group (p 0.05). Minimal surface tension was significantly lower in surfactant group compared to controls (p 0.05). Conclusions: In this model diluted surfactant administration before reperfusion attenuates the injury and improves the graft function in lung transplantation.